Optimizing Siderophore Production in Bacillus subtilis to Enhance Seed Germination and Biocontrol Efficacy against Alternaria triticina and Bipolaris sorokiniana

Introduction: Bacillus subtilis (UP11) is a gram-positive, plant growth-promoting rhizosphere bacterium (PGPR) isolated from the wheat rhizosphere. This bacterium produces siderophore, are low-molecular-weight, high-affinity molecules produced under iron-limiting conditions. This study aimed to optimize culture conditions for siderophore production and investigate the antagonistic activity against foliar blight pathogens. Work: The present study optimized the culture conditions for maximum siderophore production by evaluating various factors. The optimum pH for siderophore production was pH 7, yielding a maximum siderophore unit of 62.95%. Mannitol was identified as the best carbon source (59.14%), and ammonium nitrate as the best nitrogen source (63.04%). The presence of heavy metal Pb(NO₃)₂ in the succinate broth led to the highest yield (61.36%). The optimal iron concentration for siderophore production was determined to be 50 μM. The one-factor-at-a-time (OFAT) approach was used to investigate these parameters and their effects. Result: The optimized siderophore was partially purified using ethyl acetate extraction. This extract exhibited significant mycelial fungal inhibition, with 59.64% and 50.88% inhibition against Alternaria triticina and Bipolaris sorokiniana, respectively. The filtrate was also tested for its germination potential, demonstrating its dual role as a biocontrol and plant growth-promoter. The filtrate enhanced the percentage of germination, root and shoot length. Conclusion: Our findings indicate that Bacillus subtilis (UP11) can produce substantial quantities of siderophores, which exhibit potent antagonistic activity against foliar blight pathogens and promote plant growth. This study holds promise for advancing the development of novel biological control agents, offering the dual benefits of disease control and plant growth promotion. Siderophore producing bacteria (Bacillus subtilis) shows both antifungal and plant growth promoting activity.